1. Field of The Invention
The present invention relates to a valve assembly which may be used in an inflatable packer system. Such packer systems may be employed in a drill stem or formation testing tool. The preferred embodiment of the valve assembly is intended for use, for example, in the "Inflatable Packer System" by Felix Kuus, described and claimed in U.S. Pat. application Ser. No. 120,418, filed Feb. 11, 1980. The teachings of that application are hereby specifically incorporated by reference.
The testing tool may be used to evaluate the producing potential or productivity of an oil or gas bearing zone prior to completing a well. As drilling of a bore hole proceeds, there may be indications, such as those obtained from studying the core, which suggest the desirability of testing one or more formations for producing potential.
For the test, a testing tool is attached to the drill string and lowered into the uncased well bore to isolate the zone to be tested.
It is advantageous to have a tool that can be set at any depth in the well so that several zones can be tested, if desired, on a single trip into the well. Therefore, the valving used to control inflation and deflation of the packer(s) must be designed so that the packer(s) can be inflated and deflated repeatedly.
However, all valve functions can be mechanically controlled only by rotation of the drill string and/or by weight set-down and lifting on the drill string, since those are the only actions which can be taken from the surface.
2. Description of the Prior Art
One tool for well bore testing widley used in the industry is disclosed in U.S. Pat. No. 3,439,740 granted to George E. Conover. The Conover tool is representative of that class of packer inflation systems wherein drill pipe rotatoion actuates a piston pump which displaces fluid into the packer(s).
The Conover tool has a plurality of parts which cooperate together to perform four basic operations: (1) packer inflation by drill stem rotation; (2) flow testing by applying weight set-down on the drill string; (3) shut-in pressure testing by upward pull on the drill string; and (4) packer deflation by the simultaneous application of downward and rotational forces on the drill string to actuate a clutch which allows a mandrel to move downwardly, which in turn moves a sleeve valve downwardly, thereby allowing the packer(s) to deflate. When the packers are reset, initial rotation of the pump causes hydraulic fluid to force the sleeve valve upwardly whereupon further pumping will inflate the packers again.
The Conover tool is mechanically complex due to the functional cooperation required for flow and shut-in testing as well as inflation and deflation of the packers. For instance, the manner in which deflation of the packers is accomplished requires a complicated clutch and valving arrangement. It also requires a simultaneous application of weight and rotation to the drill string, all of which must be accomplished at the surface of the well under test.
Also in the Conover tool, there is no modularity. The pump portion and valve portion are mechanically and functionally interrelated. Therefore, in case of a pump failure or valve failure, the failure cannot be isolated to a particular module and that exchanged for a good one.